Apparatus and method for converting a pressure-supplied spray gun into an electrostatic spray gun

ABSTRACT

The invention described relates to an attachment to or adaptation of an existing spray gun which converts it into an electrostatic spray gun, by providing an electrically insulating extension of the original gun and an electrostatic supply thereto.

United States Patent Inventor Arthur Charles Mantica Epsom, Surrey,England Appl. No. 826,907

Filed May 22, 1969 Patented Dec. 7, 1971 Assignee Volstatic LimitedLondon, England APPARATUS AND METHOD FOR CONVERTING A PRESSURE-SUPPLIEDSPRAY GUN INTO AN ELECTROSTATIC SPRAY GUN I0 Claims, 2 Drawing Figs.

U.S. Cl 239/3,

239/15 Int. Cl. B05b 5/00 Field of Search 239/3, 15

[56] References Cited UNITED STATES PATENTS 3,1 I 1,266 11/1963 Axelsonet a1. 239/15 2,959,353 11/1960 Croskey et a1.. 239/15 2,995,393 8/1961Charp 239/15 X 3,265,306 8/1966 Fischer et a1. 239/15 3,268,171 8/1966Walberg 239/3 3,476,319 1 1/1969 Thatcher 239/3 X Primary Examiner-M.Henson Wood, Jr. Assistant Examiner.lohn J. Love A!!0rneyShapiro andShapiro ABSTRACT: The invention described relates to an attachment to oradaptation of an existing spray gun which converts it into anelectrostatic spray gun, by providing an electrically insulatingextension of the original gun and an electrostatic supply thereto.

I 12 13 I m 24 #1 11 111111 E "int-ii q l liriifxl'g-l H 5 PATENTED 0H:1 Ian SHEET 1 [IF 2 PATENIED DEC 7 IBTI SHEET 2 BF 2 mm Q \w a APIPATUSAND METHOD FOR CONVIER .1 It A PRESSURE-SUPIPUED SPRAY GUN KN'EQ ANELECTROSTATKC SPRAY GUN This invention relates to spraying apparatus andmore particularly to spraying apparatus for paint spraying using the airless electrostatic system.

Previously proposed systems for airless electrostatic spraying havenecessitated the purchase of entirely new equipment, and conversion fromairless, i.e., purely pressurized, spraying to electrostatic airlessspraying has involved considerable expense.

The present invention seeks to provide apparatus in the form of anattachment for a conventional airless pressureatomizing spray gun whichwill readily convert it into an electrostatic airless spray gun, theonly additional apparatus required apart from the attachment being theelectrostatic generator.

According to the invention, apparatus for such conversion comprises afirst body of electrically insulating material having a longitudinalbore therethrough, one end of the body being adapted for attachment toan existing spray gun in place of the usual nozzle and the other end ofthe body having a spray nozzle thereon supplied by the bore, and asecond body attached to the first body and of electrically insulatingmaterial, the second body having a high voltage cable passingtherethrough adapted to be connected at one end to a high voltage sourceand at the other end to a discharge probe which extends into thevicinity of the spray emerging from the spray nozzle.

Preferably the end of the first body adapted for attachment to the spraygun is provided with a hollow bolt which is passed through the nouleretaining nut on the spray gun and screwed into the first body to retainthe nozzle retaining nut thereon, the nozzle retaining nut then beingscrewed back onto the spray gun to attach the attachment thereto.

One embodiment of the invention will now be described by way of example,with reference to the accompanying drawings, in which:

FlG. l is a perspective view of the attachment of the invention attachedto a conventional airless spray gun; and

H6. 2 is a side sectional view of the attachment shown in FIG. ll.

Referring to the drawings, there is shown a spray paint gun I having aconnection 2 with a pipeline 3 for the pressurized supply of paint (orsupply of other sprayable material to be sprayed). At the outlet of thegun I there is provided in place of the usual atomizer jet nozzle,deemed to have been removed, a hollow bolt 4.

This hollow bolt 4 has threaded into it the retaining nut 5 of the spraygun I and is screwed into the original gun thereafier being locked bythe nut 5. The bolt 4 is also screwed into an electrically insulatingbody 7, preferably of plastics, and is locked thereto by a nut 6. Thebody 7 has a central bore h communicating at one end with the bore ofthe hollow bolt 4, and at the other end with a bored double threadedmember 9, of which one end screws into the bore 8. A locking nut 10 isprovided to lock the member 9 to the body 7.

On to the other end of the member 9 is screwed a nozzle retaining nut 11retaining on the outer end of the member 9 an atomizing nozzle 12 and awasher 13, the vicinity of this nozzle being subjected to anelectrostatic field so that the liquid sprayed is influenced thereby.The nozzle 12 can be of any suitable form and may in fact be the nozzlewhich was originally used with the spray gun 2.

Attached to the body 7 by any suitable means such as adhesion,strapping, soldering, or other convenient means (not shown) is a secondbody M; the body l4 may be made integral with the body 7. This secondbody 141 is bored and contains a high voltage cable 15 which isconnected to an electrostatic generator (not shown). The cable 15 isconnected to a current limiting resistor 16, which for this purpose isheld against the cable end by a spring 17, the spring and resistor beingretained in the body 14 by a screw cap 18 provided with a socket 119into which an electrostatic probe unit 20 fits.

The probe unit consists of an electrically insulating body 2!, connector22 which fits into the socket l9 and a probe 23 having a needle point241 and electrical insulation 25. As can be seen, the probe ispositioned so that its point 24 is adjacent to and spaced from theoutlet of the nozzle H2. The nozzle 12, as is usual, has a diametricgroove or slot in which the point 24 may be located.

To adapt a conventional spray gun, the following procedure is carriedout:

The bolt 4 is removed from the body 7, after slacking the nut 6. Theretaining nut 5 on the gun is unscrewed and the nozzle (which may be thenozzle 112) is removed therefrom. Next, the nut 5 having been threadedon the bolt 4 the bolt 4 is screwed into the body 7, and a locking nut 6having been threaded on the bolt 4 is tightened on the bolt, to lock itin the body 7. The bolt 4 having been screwed into the body 7, the nut 5is tightened back against the body 7, thus providing locked connectionbetween the original spray gun and the attachment.

Next, the retaining nut 111 is unscrewed and the nozzle 12, which mayhave been removed from the original spray gun, is

placed therein and retained on the member 9 by screwing up the nut 11.The electrode 24 is now adjusted into its required position with respectto the noule 12.

The apparatus is then ready for use as soon as it is supplied with paintvia the pipeline 3 and with a high voltage via the cable 15.

To revert to the original gun, the reverse procedure is adopted.

it will be understood that various modifications can be made to theabove-described embodiment without departing from the scope of theinvention. For example, the two bodies 7 and M can be made as oneintegral unit. Full adjustment may be provided for the probe so as toproduce optimum performance in widely varying conditions. Sometimes itmay be found desirable to have the probe some 3 to 4 inches from thespray nozzle opening. This is useful when spraying paints of lowelectrical resistance since it prevents an unnecessary voltage dropalong the paint line.

The attachment may be provided with a switch operable for example by theoriginal trigger mechanism of the gun I, illustrated in FIG. 1, forcontrolling the energization of the probe.

1 claim:

1. A method of converting an existing pressure-supplied spray gun,having an original spray nozzle and retaining means for attaching saidoriginal spray nozzle to said existing spray gun, into an electrostaticspray gun, comprising:

providing a first electrically insulative body having a bore extendingfrom one end thereof to the other end thereof, attachment means at saidone end, and means for mounting nozzle means at said other end, a secondbody attached to said first body having an electrical lead housedtherein, and an electrically conductive probe supported by one of saidfirst and second bodies and extending into the vicinity of said nozzlemeans when said nozzle means is attached to said other end;

disengaging said retaining means and removing said original spray nozzlefrom said existing spray gun; engaging said attachment means with saidretaining means for attaching said first body to said retaining means inlieu of said original spray nozzle; and

engaging said nozzle means with said mounting means to attach saidnozzle means to said other end of said first body.

2. A method according to claim ll, wherein said noule means is saidoriginal spray nozzle.

3. A method of converting an existing pressure-supplied spray gun,having an original spray nozzle and retaining means for attaching saidoriginal spray nozzle to said existing spray gun, into an electrostaticspray gun, comprising:

providing an electrically insulative body having a bore extending fromone end thereof to the other end thereof, attachment means at said oneend, and means for mounting nozzle means at said other end, and meanssupporting an electrically conductive probe extending into the vicinityof said nozzle means when said nozzle means is attached to said otherend;

disengaging said retaining means and removing said original spray nozzlefrom said existing spray gun;

engaging said attachment means with said retaining means for attachingsaid body to said retaining means in lieu of said original spray nozzle;and

engaging said nozzle means with said mounting means to attach saidnozzle means to said other end of said body.

4. A method as claimed in claim 1, in which the first body and thesecond body are made as one integral unit.

5. A method according to claim 1, in which the second body contains acurrent-limiting resistor in series with the electrical lead.

6. A method according to claim 1, in which said noule means comprises ajet nozzle opening, and said probe is between 3 inches and 4 inches fromsaid jet nozzle opening.

7. A method according to claim 1, in which said attachment meanscomprises a hollow bolt having screw threads engageable with screwthreads provided on said retaining means to bring said bore intocommunication with sprayable material supplied by said existing gun.

8. A method according to claim 7, in which said bore is provided withthreads at said other end for. engagement with threads on said nozzlemeans.

9. A method according to claim 1, in which said second body includesmeans providing a cable conduit for said electrical lead and meansconnecting said electrical lead through a current-limiting resistor tosaid probe.

10. A method according to claim 1, in which said electrically conductiveprobe is supported by said second body.

* i i t i

1. A method of converting an existing pressure-supplied spray gun,having an original spray nozzle and retaining means for attaching saidoriginal spray nozzle to said existing spray gun, into an electrostaticspray gun, comprising: providing a first electrically insulative bodyhaving a bore extending from one end thereof to the other end thereof,attachment means at said one end, and means for mounting nozzle means atsaid other end, a second body attached to said first body having anelectrical lead housed therein, and an electrically conductive probesupported by one of said first and second bodies and extending into thevicinity of said nozzle means when said nozzle means is attached to saidother end; disengaging said retaining means and removing said originalspray nozzle from said existing spray gun; engaging said attAchmentmeans with said retaining means for attaching said first body to saidretaining means in lieu of said original spray nozzle; and engaging saidnozzle means with said mounting means to attach said nozzle means tosaid other end of said first body.
 2. A method according to claim 1,wherein said nozzle means is said original spray nozzle.
 3. A method ofconverting an existing pressure-supplied spray gun, having an originalspray nozzle and retaining means for attaching said original spraynozzle to said existing spray gun, into an electrostatic spray gun,comprising: providing an electrically insulative body having a boreextending from one end thereof to the other end thereof, attachmentmeans at said one end, and means for mounting nozzle means at said otherend, and means supporting an electrically conductive probe extendinginto the vicinity of said nozzle means when said nozzle means isattached to said other end; disengaging said retaining means andremoving said original spray nozzle from said existing spray gun;engaging said attachment means with said retaining means for attachingsaid body to said retaining means in lieu of said original spray nozzle;and engaging said nozzle means with said mounting means to attach saidnozzle means to said other end of said body.
 4. A method as claimed inclaim 1, in which the first body and the second body are made as oneintegral unit.
 5. A method according to claim 1, in which the secondbody contains a current-limiting resistor in series with the electricallead.
 6. A method according to claim 1, in which said nozzle meanscomprises a jet nozzle opening, and said probe is between 3 inches and 4inches from said jet nozzle opening.
 7. A method according to claim 1,in which said attachment means comprises a hollow bolt having screwthreads engageable with screw threads provided on said retaining meansto bring said bore into communication with sprayable material suppliedby said existing gun.
 8. A method according to claim 7, in which saidbore is provided with threads at said other end for engagement withthreads on said nozzle means.
 9. A method according to claim 1, in whichsaid second body includes means providing a cable conduit for saidelectrical lead and means connecting said electrical lead through acurrent-limiting resistor to said probe.
 10. A method according to claim1, in which said electrically conductive probe is supported by saidsecond body.